be ‧ liev ‧ er /bəˈliːvə, bɪˈliːvə $ -ər/ BrE AmE noun [countable]
[ Word Family: noun : ↑ belief , ↑ disbelief , ↑ believer ; adjective : ↑ believable ≠ ↑ unbelievable , ↑ disbelieving ; verb : ↑ believe ≠ ↑ disbelieve ; adverb : ↑ unbelievably ]
1 . be a (great/firm) believer in something to believe strongly that something is good and effective:
I’m a great believer in regular exercise.
2 . someone who believes in a particular god, religion, or system of beliefs OPP unbeliever